Automatic classification of communication signals has not been achieved in any practical sense prior to the present invention. This is so in spite of the fact that there is a definite need for such equipment on the part of many users, such as government agencies, to monitor portions of the communication spectrum. The general problem of automatic signal classification seems at first to be a rather simple task. Most radio operators can learn in rather short order to recognize and classify specific signals with the aid of time representations, spectral displays, audio characteristics, and the like. However, the translation from those classifying operations performed mentally to a set of specific instructions to be performed by a machine is a difficult problem indeed. This is a problem of long-standing interest that has eluded a systematic approach to solution. Although there have been numerous investigations concerning pattern recognition techniques, most of these are directed at specific problems, which have limited extension to other problems, or to those utilizing complex adaptive techniques, which are rather difficult to analyze theoretically. As a result, there does not yet exist a general unifying concept, or basic method of approach to problems in the field of automatic pattern recognition.
Automatic signal classification is thus not a singular problem, but rather is a composite consideration of the following broad categories: Establishing a desirable model to fit the specific problem statement; Specification of a set of measurements to be performed on the electrical signals; and Characterization of the recognition techniques that exploit the differences in the measurement values.
It is therefore an object of the present invention to provide a method and apparatus for automatically classifying communication signals received at a receiver.
In providing signal classifier equipment that is capable of operating in conjunction with a wide variety of receiver it is necessary to render the equipment adaptable to accommodate different intermediate frequencies as well as variations in amplitude and phase of the incoming signal.
It is another object of the present invention to provide an interface technique for adapting the signal classifier to substantially any communication receiver.